The present invention relates to a magnetic recording medium for attaining high-density magnetic recording and a magnetic storage device combined with a magnetic storage head.
The demand for a larger capacity magnetic disk drive is becoming more and more keen. To meet this demand it is required to develop a magnetic head of high sensitivity and a magnetic recording medium having a high S/N ratio. To improve the S/N ratio of a magnetic recording medium it is necessary to improve the read output for high-density recording. Generally, the magnetic recording medium comprises a first underlying layer called a seed layer formed on a substrate, a second underlying layer of a body-centered cubic structure formed of an alloy containing chromium as a main component, a magnetic film, and a protective film containing carbon as a main component. The magnetic film is formed of an alloy with a hexagonal close-packed structure containing cobalt as a main component. To improve the read output it is effective to let the magnetic film have a crystal orientation such that (110) plane or (100) plane is nearly parallel to the substrate surface and let the c-axis of the hexagonal close-packed structure be an axis of easy magnetization facing in the in-plane direction. It is known that the crystal orientation of the magnetic film can be controlled by the seed layer. As a technique for attaining both thermal stability and low noise there is disclosed in Patent Literature 1 (Japanese Patent Laid-open No. 7-134820 (p. 3)) a magnetic recording medium wherein an underlying layer is formed on a substrate and at least two magnetic layers of different compositions are formed in contact with each other on the underlying layer to constitute a laminated magnetic film, the laminated magnetic film being provided in multiple layers through a non-magnetic layer such as a ruthenium layer. As a technique for improving the crystallographic orientation of a magnetic layer there is disclosed in Patent Literature 2 (U.S. Pat. No. 6,150,015) a magnetic thin film having an ultra-thin nucleating layer formed of a Co—Cr-base alloy deposited at a low deposition rate of not higher than 1 Å/sec. and a recording layer formed of a Co—Cr—Pt-base magnetic alloy deposited at a high deposition rate. As a technique for improving the output characteristic of a magnetic recording medium there is disclosed in Patent Literature 3 (Japanese Patent No. 3576372) a magnetic recording medium comprising a non-magnetic underlying film, a magnetic film and a protective film formed in this order on a substrate, the non-magnetic underlying film being formed of a Cr or Cr alloy, the magnetic film comprising a plurality of magnetic layers of a Co alloy containing Cr, the magnetic layers having Cr contents which become gradually lower from lower to upper magnetic layers.